“…In 1962, Plotz and Davis demonstrated synergism between penicillin and streptomycin for Escherichia coli, and presented evidence that the basis of this interaction was the increased penetration into the bacterial cell by the aminoglycoside as a result of penicillin-induced, sublethal damage to the bacterial membrane (23). Other investigators have demonstrated synergistic interaction between penicillin, ampicillin, and' carbenicillin or other semisynthetic penicillins plus various aminoglycosides against several Enterobacteriaceae, including species of Proteus, Klebsiella, Enterobacter, and Serratia (5,6,10,14,29,30).…”